title: Spin-induced optical conductivity in the spin-liquid candidate herbertsmithite.
abstract: We report a direct measurement of the low-frequency optical conductivity of large-area single-crystal herbertsmithite, a promising spin-liquid candidate material, by means of terahertz time-domain spectroscopy. In the spectral range below 1.4 THz, we observe a contribution to the real part of the in-plane conductivity σ(ab)(ω) from the spin degree of freedom. This spin-induced conductivity exhibits a power-law dependence on frequency σ(ab)(ω) ~ ω(β) with β ≈ 1.4. Our observation is consistent with the theoretically predicted low-frequency conductivity arising from an emergent gauge field of a gapless U(1) Dirac spin liquid.
authors.affiliation: Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: D V
authors.initials: DV
authors.lastname: Pilon
authors.forename: C H
authors.initials: CH
authors.lastname: Lui
authors.forename: T-H
authors.initials: TH
authors.lastname: Han
authors.forename: D
authors.initials: D
authors.lastname: Shrekenhamer
authors.forename: A J
authors.initials: AJ
authors.lastname: Frenzel
authors.forename: W J
authors.initials: WJ
authors.lastname: Padilla
authors.forename: Y S
authors.initials: YS
authors.lastname: Lee
authors.forename: N
authors.initials: N
authors.lastname: Gedik